1. Field of the Invention
The present invention relates to a method for evaluating roughness on a silicon substrate surface with nanometer scale resolution.
2. Description of the Related Art
Roughness on a silicon substrate degrades electrical properties of a thin oxide films. Therefore, it is necessary to control and evaluate the surface roughness with nanometer scale resolution when a highly integrated circuit is manufactured. Conventionally, the surface roughness of the silicon substrate is evaluated by observing a cross section of the substrate using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), or by scanning the substrate surface using a probe of a scanning tunneling microscope (STM) or an atomic force microscope (AFM).
According to the conventional methods, a region in which the surface roughness can be evaluated is small. For example, when the surface roughness is evaluated with nanometer scale resolution using the SEM or TEM, the sectional region which can be observed at one time is approximately several hundreds .ANG.. In a case of using the STM or AFM which scan the surface with the probe, a region of only several tens .mu.m square is measured, so that it is difficult to evaluate the surface roughness with nanometer scale resolution over a large area.